1. Field
The described technology relates to systems and methods of retopologizing graphical information representing a polygonal data object.
2. Description of the Related Technology
Polygonal model data is created with, for example a 3-D CAD software tool by, for example, a designer. Polygonal model data may alternatively be created by or with a scanning system which scans an object and creates data representing the surface of the object. The polygonal model or polygonal mesh includes discrete data points describing one or more surfaces or objects. The polygonal (or geometric) model, or data object, includes a number of geometrics, such as vertices, edges, and faces. Polygonal models are convenient for design work at least because they define the surface or object with a degree of detail convenient for the designer to work with. The shape of the surface or object is described by the data points, and the surface between the data points is perceived, but is not necessarily represented in the data. This allows for the CAD system to function quicker because of a significantly reduced data set representing the surface or object, while providing the designer enough detail to perceive and manipulate to achieve a desired design.
The polygonal data may be edited by a designer according to the designer's purposes. For example, the designer may add features to the object represented by the polygonal data using mesh operations. In addition, to create smooth, natural looking objects, a smoothing algorithm may be used to modify the polygonal data. For example, a Catmull-Clark algorithm or a Loop subdivision algorithm may be performed on the polygonal data. The smoothing algorithm modifies the polygonal data by, for example, adding vertices and repositioning existing vertices. Thus, the smoothing algorithm generates a modified object.
Typically, certain polygonal data is preferred for editing or smoothing. For example, polygonal data having predominantly quadrilateral faces with vertices predominantly connected to four edges may be preferred. In addition, for convenience in editing and computer system data management, the polygonal data may preferably have geometry density commensurate with the topological variation in each region of the model. For example a substantially planar region would preferably have fewer geometries per unit area than a region which has intricate topological detail.
Retopologizing may be performed to convert polygonal data of a less desirable constitution to a more preferred state. Data having many small triangular faces such as a scanned mesh generated by a scanning system may be retopologized to create a mesh having significantly fewer quadrilateral faces. Brep data, subdivided data, a triangular mesh, volumetric representation data, quad-tree data, oct-tree data, or other data may also be preferably retopologized.
In some embodiments of retopologizing, the process is manual, where a user selects locations for geometries, such as vertices, of the retopologized data. The designer indicates to the computer system locations for added vertices in the plane of view as displayed, and the computer system causes the added vertices to be on the surface of the object being retopologized. Each vertex may be individually placed, and faces generated based on the placed vertices. Such a process is cumbersome and slow.